1. Technical Field
The invention relates to a device for administering an injectable product in doses.
2. Description of the Related Art
A device such as the invention relates to is known, for example, from WO 97/36626. This device comprises a casing, comprising a reservoir for the product. Accommodated in the reservoir is a piston which, when moved in a feed direction towards an outlet of the reservoir, forces product out of the reservoir. A gear rack, which pushes against the piston, moves the piston in the feed direction. The gear rack is provided with series of teeth. In the casing, a drive member is furthermore accommodated, movable in and counter to the feed direction relative to the casing, said drive member slaving the gear rack when moved in the feed direction. For this purpose, the drive member meshes with the series of teeth in the gear rack via slaving means. When moved, only one of the slaving means is ever pushing against the back of a tooth of a series of teeth. For setting the amount of product administered by one piston stroke, the drive member in a front position is manually retracted counter to the feed direction by a set dosage path length, the slaving means of the drive member thereby sliding over the series of teeth and giving elastically. The gear rack is prevented from being moved backwards by blocking means accommodated secured against shifting relative to the casing. The blocking means cooperate with one of the series of teeth of the gear rack, such that the blocking means prevent the gear rack from being moved counter to the feed direction and allow the gear rack to be moved in the feed direction by giving elastically. When the gear rack is moved, the blocking means do not fully mesh with the tooth gaps of the series of teeth simultaneously. Only one of the blocking means is ever meshed with a tooth gap, while another is elastically bent away, pushing against the flank of a tooth.
The alternating mesh during movement in the feed direction, advantageous with respect to accuracy and safety during dosing and administering, loses this advantage after a lengthy storage period, which from factory to initial use usually amounts to several months, or does not even take effect, due to material fatigue in a blocking or slaving means bent away during storage.
It is an object of the invention to assure, with great certainty, precise dosing and administering of the product, even after a lengthy storage period, in such a device for administering an injectable product in doses.
The object is solved by the subject of the independent claims.
A device for administering an injectable product in doses comprises a casing, comprising: a reservoir for the product; a piston, which when moved in a feed direction towards an outlet of the reservoir forces product out of the reservoir; a gear rack, moving the piston in the feed direction, comprising a first series of teeth and a second series of teeth; a drive member, movable relative to the casing in and counter to the feed direction, and slaving the gear rack when moved in the feed direction; and a blocking means, arranged secured against shifting relative to the casing and cooperating with one of the series of teeth, such that it prevents the gear rack from being moved counter to the feed direction and allows the gear rack to be moved in the feed direction.
Preferably, at least two blocking means are provided, which do not fully mesh with the tooth gaps of the series of teeth simultaneously. Only one of the blocking means is ever meshed with a tooth gap, while the other is elastically pushed away, pushing against the flank of a tooth perpendicular to the feed direction.
In accordance with the invention, at least one of the at least two series of teeth of the gear rack comprises an elongated tooth gap, with which the blocking means cooperating with said series of teeth meshes, when the gear rack assumes a starting position prior to a first administering. The drive member and the gear rack assume the starting position relative to each other after assembly and up until a first administering. Thus, in the starting position, each of at least two blocking means meshes with a tooth gap. By maintaining the alternating mesh, advantageous for administering, material fatigue in the blocking means is prevented.
Preferably, at least two slaving means are connected secured against shifting to the drive member, each of them cooperating with one of the series of teeth, such that only one of the at least two slaving means is pushed in the feed direction against a tooth of the gear rack when the drive member is moved in the feed direction, while the other elastically gives on the flank of a tooth. By giving elastically, the slaving means allow the drive member to be moved counter to the feed direction and relative to the gear rack.
In accordance with the invention, at least one of the at least two series of teeth of the gear rack comprises an elongated tooth gap, with which the slaving means cooperating with this series of teeth meshes when the gear rack assumes the cited starting position prior to a first administering. In this way, material fatigue in the slaving means is prevented.
An elongated tooth gap is understood as a tooth gap which, when viewed in the feed direction, is longer than the other, regularly provided tooth gaps in the series of teeth, which will be termed regular tooth gaps in the following. A blocking or slaving means is able to mesh with the elongated region in a longer region than in regular tooth gaps, preferably with the same depth of mesh as when the blocking means meshes with a regular tooth gap in the blocking position or as when the slaving means meshes with a regular tooth gap in the abutting position. The mesh is in any event fuller than would be the case if a regular tooth gap opposed the blocking or slaving means in the starting position. A mesh is accordingly termed full mesh when a blocking or slaving means protrudes right into the root of an interdental space, or when a blocking or slaving means protrudes towards the gear rack to the same extent as in a blocking or abutting position.
It is particularly preferred in the starting position that both an elongated tooth gap for at least one of the at least two blocking means as well as an elongated tooth gap for at least one of the at least two slaving means are provided in the at least two series of teeth. The elongated tooth gap for the blocking means and the elongated tooth gap for the slaving means may be provided in a single series of teeth. It is, however, also possible for the one elongated tooth gap to be provided in one series of teeth and the other elongated tooth gap in the other series of teeth.
The series of teeth of the gear rack are preferably serrated, comprising teeth which taper in the feed direction. The blocking and slaving means is/are preferably adapted in shape, such that pushing away is hindered as little as possible by friction when the gear rack is moved in the feed direction, and movement counter to the feed direction is securely blocked by a purely positive mesh. In principle, however, the series of teeth may also show a different shape, as long as the two requirements of allowing movement in the feed direction and securely preventing movement counter to the feed direction are fulfilled.
The series of teeth are preferably provided opposite or also adjacent to each other on the gear rack; in principle, however, they could be provided in any region of the gear rack with a corresponding height offset in the blocking and/or slaving means. The slaving means, however, are preferably arranged level with each other, and the alternating mesh achieved by offsetting the series of teeth by a fraction of a pitch. The blocking means are likewise preferably arranged level with each other.
The slaving means and the blocking means work in the same way to fulfill their respective functions, by abutting against the back of a tooth of the gear rack and so slaving or blocking the gear rack, and allowing the gear rack to be retracted or advanced, by giving elastically. They may be provided identically or differently. Elastic give is preferably achieved by bending a tongue extending in the direction of movement, perpendicular to the direction of movement of the gear rack. In principle, it would also be possible, for example, for a cam to be mounted, perpendicularly movable against the elastic restoring forces.
In one embodiment variant, the gear rack is equipped with a third series of teeth with which a third blocking means meshes, wherein the third blocking means also does not mesh with a tooth gap of the gear rack simultaneously with the at least two other blocking means. Preferably, a fourth series of teeth is also provided at the same height on the gear rack, with which a fourth blocking means meshes. In accordance with the invention, the third series of teethxe2x80x94and in the case of a fourth series of teeth, the fourth series of teethxe2x80x94also comprises an elongated tooth gap with which the respective blocking means meshes in the starting position of the gear rack.
In a preferred example embodiment, including a third series of teeth, the drive member preferably comprises a third slaving means. The third slaving means of the drive member also does not mesh with a tooth gap of the gear rack simultaneously with the at least two other slaving means of the drive member, such that it pushes against a tooth of the gear rack when moved in the feed direction. The three slaving means mesh alternately. If a fourth series of teeth is provided, the drive member preferably comprises a fourth slaving means.
Thus, a particularly finely adjusted alternating mesh of the blocking and/or slaving means is possible, while still preventing material fatigue due to lengthy storage.
In one embodiment variant, the at least two blocking means mesh with the at least two series of teeth of the gear rack, while two slaving means of the drive member mesh with two other series of teeth of the gear rack. Through the resulting alternating arrangement of the slaving means and blocking means around the gear rack, it is possible to shorten the length of the gear rack and thus the length of the device. The blocking and slaving means may be provided at the same height with respect to the feed direction. An alternating mesh of the blocking means among each other and of the slaving means among each other is nonetheless possible. The Applicant reserves the right to seek separate patent protection for the device with and without the form of an elongated tooth base.